Information For The New Harley Owner:
Plan Your Attack
This article is a must for the new Harley owner. “New Harley Owner” meaning anyone that has purchased a Harley and is thinking about performance upgrades. The performance articles on this website coincide with each other. The article will touch on most of the subjects covered in those articles.
The most important thing to remember is that the key to making a lot of power is in choosing the correct matching components and not necessarily choosing the biggest components.
I want to start by thanking everyone for their support and the supportive e-mails and comments showing appreciation of this website.
I personally don’t care about the HP (Horse Power) ratings when it comes to Harley motorcycles. I do care about TQ (Torque). TQ is the “G” force that you feel when the bike is pulling hard during acceleration. HP keeps the momentum of the TQ going. Think of it this way: If you had six people pushing a car on a flat road from a dead stand still. After it got rolling, it would probably only take three people to keep it going. In this example the six people are representing TQ and the three people are representing HP. While pushing the vehicle on the flat road, you suddenly come to a hill. Do you want to keep the three people (HP) to push you up the hill or would you like to use the six people (TQ) to push the vehicle up the hill.
I said all of that to show the importance of TQ. Here is one thing to also remember: HP will follow TQ. If you increase the TQ the HP will also increase. Here is why: A dynamometer uses this formula to calculate HP. TQ x RPM / 5252 = HP. Look at any dyno graph and pick a RPM and see what the TQ is at that RPM. Now multiply the TQ by the RPM. Divide the product by 5252 and it will give you the HP at that RPM. If it doesn’t, then you need to question the accuracy of the graph.
Most high HP engines are designed to have the peak TQ further up the RPM range. Take the graph from above and move the peak TQ 1000 RPM up the RPM range and do the same calculations and see how the HP increases. Peak TQ was 103.7 @ 3600 RPM. The HP @ 4600 RPM is currently 85 HP. Multiply the peak TQ (103.7) x 4600 RPM divided by 5252. The HP @ 4600 RPM would change from 85 HP to about 91 HP. This increased the HP, but it takes longer to get to that 91 HP.
Going back to the illustration of pushing the vehicle up a hill…why do you have to gear down on your motorcycle to go up a hill? The answer is very simple. You have to get in the RPM range where the TORQUE is located. These heavy bikes were designed to produce low RPM TQ, not high RPM HP. So why not enhance what the bike was designed for instead of revving the crap out of the bike to get to the power band.
Torque Torque and more Torque!
Horse Power is for winning Dyno Shootouts. Torque is for winning races and beating your buddy from stop light to stop light or pulling away from your buddy with a fourth gear roll on. I know what you are thinking…My bike has won all of those dyno shootouts. I actually designed the engine for TQ. Remember earlier when I said that HP will follow TQ. So why not take advantage of the HP when generating so much TQ? Remember that my bike has around 20 more in TQ than it does in HP.
Crotch rockets are light, which enables them to design the engines with the peak TQ very far up the RPM range. They usually have twice as much HP as they have TQ. Take a dyno sheet from a high HP crotch rocket and move the TQ way down the RPM range (around the same TQ peak as a Harley) and use the HP formula described earlier (TQxRPM/5252) then watch the TQ increase and the HP decrease. Moving the TQ way up the RPM range works well for the light 400 - 500 lb. crotch rockets, but add the weight difference of the Harley such as a bagger and see just how fast it will be then. It will still have a high MPH, but it will take a long time to get there.
Watch this video of my bike racing against crotch rockets. I out ran them with TQ, not HP. At the time that this video was shot, the bike stopped making HP at 5500 RPM.
When planning your performance upgrades, target high TQ, not HP. In this article I will give suggestions of what components to use to increase TQ. I will also explain briefly why these parts increase TQ. For more detailed information, there will be links to other articles that will explain the theories further.
When choosing a cam set, look for a cam that has a short duration (no more than 240 degrees) with an early intake valve closing no later than 20 degrees. There are several good high torque cams on the market.
When choosing a cam, be sure to choose a cam with enough lift that will work well with future performance modifications. The valve size and lift will determine what RPM that the engine will be capable of making HP. Click here for more information on the MACH Index. When using stock intake valves (1.8”) you will need at least a .550” lift to make HP up to 5500 RPM.
If you decide to increase the engine size to 103 ci, the .550” lift cam will only be able to produce HP up to 5000 RPM. You would need to increase the intake valve size to 1.9” or increase the cam lift to .575 to make HP up to 5500 RPM. Also keep in mind anytime that you increase the cam duration, you will lower the Dynamic Compression Ratio.
Here is a link to an online MACH Index calculator.
http://www.wallaceracing.com/machcalc.php
Choose a good 2 into 1 exhaust. The 2 into 1 pipe will create more TQ. The true dual exhaust may sound good, but they won’t make the TQ like a 2 into 1 pipe. Another thing to consider when choosing an exhaust is that an exhaust may work well with a certain cam timing, but may not perform well with a different cam timing. The timing of the exhaust valve closing HAS to match the timing of the exhaust waves. This is why when you change the exhaust and the bike makes less power. For more information on this subject, click this link.
Use a good free flow air cleaner. The volume of the air cleaner can also affect the power. Click here for more information.
Anytime that you add performance upgrades, you will need to have the fuel injection remapped. The SE Race Tuner, Super Tuner and the TTS Tuner are the better tuners on the market. They have more manipulation capabilities than the other tuners on the market.
In conclusion: I would suggest that you choose a cam such as the Woods TW-7H if you are planning to increase the cubic inch to 103. You can use a cam such as the SE-255 if you are not planning on a 103 ci increase. Use a good 2 into 1 pipe such as the D&D Fat Cat, D&D Boss, V&H Pro Pipe, R&B LSR pipe.